Speed regulating system



H. R. A. HANSEN SPEED REGULATING SYSTEM Filed March l, 1960 June 4, 1963 United States Patent O 3,092,766 SPEED REGULATNG SYSTEM Hans R. A. Hansen, Milwaukee, Wis., assigner to The Louis Allis Co., Milwaukee, Wis., a corporation ot' Wisconsin Filed Mar. 1, 1960, Ser. N 12,261 4 Claims. (Cl. S18-$41) The present invention relates to control systems and, in particular, to control systems tfor regulating the speed of an electrical driving apparatus.

It is an object of the present invention to provide a ynew and improved control system that accurately regulates the speed of an' electrical apparatus.

it is another object of the present invention in accordance with the previous object to regulate the amount of voltage supplied to the armature of an electrical driving apparatus.

lt is a further object of the present invention to provide a sensitive and accurate control system for instantaneously accelerating or decelerating an electrical driving apparatus.

It is yet another object of the present invention to provide a control system that provides iniinitely adjustable, speed regulation `for an electrical driving apparatus.

It is another object of Ithe present invention to regulate the speed of an electrical driving apparatus by providing a control system which is embodied in the armature circuit of the driving apparatus.

it is yet another object of the present invention to provide a control system that controls the average voltage supplied to the armature circuit of an electrical driving apparatus, thereby to regulate its speed.

It is a further object in accordance with the previous object to control the time :duration of voltage pulses sup.- plied to the armature circuit in order to control the average armature volta-ge and thereby regulate the speed of the apparatus.

The above and other objects are realized in accordance with the present invention by providing a new and irnproved control system for an electrical driving apparat-us, `for example a DC. motor. The control system is sensitive and accurate in operation and provides ininitely adjustable, speed regnilation for the motor. The system is associated with the armature circuit of the DC. motor and, to this end, supplies a plurality of Voltage pulses to the armature circuit. The voltage pulses produce an average armature voltage which in accordance with the well known motor principle, i.e.,

VA rpm. (i) determines the speed of the motor (r.p.m.=speed, VAzarmature voltage, and rpzflux of lield winding). In order to change the speed of the motor, the average armature voltage is either increased or decreased by changing the character of the voltage pulses, for example, by changing the time duration of the voltage pulses. The control system is able -to smoothly start the motor from a dead stop with an optimum designated acceleration. The acceleration of the motor is controllable and the speed is infinitely adjustable, i.e., the system can be adjusted to cause the motor to rotate at any one of an intinite number of speeds between o and maximum rated speed.

.The invention, both as to its organization and method of operation, taken with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawing, in which:

FIGURE 1 is a schematic view of a control system, embodying the features of the present invention, and of a series D.C. motor operatively Iassociated with the system;

FIG. 2 is a schematic View of the control system of FIG. 1 and of a shunt D.C. motor operatively associated with the system; and

FIGS. 3A, 3B, 3C and 3D are graphic views of wave foi-,ms at selected points in the control system of FIG. l.

Referring now to the drawing, a control system embodying the principles of the present invention is illustrated in' both FIGS. 1 and Zand is `identified by reference numeral 10. The control system operates to regulate the speed of an electrical driving apparatus, for example, 'a DC. electric motor; it has particularly utility in controlling a D.C. motor drivingly associated with a golf cant or the like. The control system has proven to be an inexpensive land dependable speed-regulating arrangement for the golf cart motor, but since the control system has a wide range of applications, the present invention should not 4be construed as being limited -to use with a golf cart motor.

In any event, the control system lil is illustrated in FIG. 1 as controlling the speed of a D.C. motor of the series type, while the control system 10 is illustrated in FIG. 2 as controlling the speed of a D.C. motor of the shunt type. In each application, the control system l@ is associated with the armature circuit of the DC. inotor and is operative to produce a plurality of repetitive DC. voltage pulses as shown' in FIG. 3D which develop Ian average voltage for `the armature circuit. By suitable adjustment of the control system 10, the characteristics of the voltage pulses can be changed, for example, the width of each pulse can be altered as explained hereinafter with regard to FIGS. 3A to 3D, :thereby changing the average armature voltage of the motor. Since the speed of the motor is directly proportional to the armature voltage, the speed of the rnotor is immediately changed in response to adjustment of the :control system itl.

Referring now to FIG. l in greater detail, the D.C. motor i2, which is regulated by the control system lil, is of conventional construction and embodies a series armature winding 14, illustrated diagrammatically, and a series field winding 16 serially connected with the armature winding 14 by a suitable conductor 1S. As is well known, the direction of rotation of the motor 12 is dependent upon the direction of current flow through the field winding 16 and, in this connection, a reversing switch 29 is employed to reverse the connections of the eld winding 16. More specifically, if clockwise rotation, for example, of the motor is desired, the contacts 20a of the switch 20 are closed, thereby to electrically connect the field winding end 16a to the armature winding 14 and the field winding end -16b to a conductor 22. On the other hand, if counterclockwise rotation of the motor is desired, the contacts 2019 of switch 2u are closed, thereby to connect the iield winding end ltb to the armature winding r1.4 :and the iield winding end 16a to the conductor `22. irrespective of the way in which the field winding 16 is connected, the circuit for the -iield winding 16 and the armature winding are serially connected `together, the field winding )i6` being connected via conductor 22 to the negative side of a battery 2S and the armature winding :14 being connected via conductor 30 to the control system lil. To complete the circuit, the control system 10 is connected via conductor 36 to the positive side of the battery 28.

The control system 1d, in operation, actually modifies the -D.C. voltage developed by the battery 28 and, accordingly, controls the voltage that appears across the armature winding 14 of the motor 12. More specifically, the system 10 comprises .a regulating section 32 connected in shunt across the power supply 2S, i.e., between the conductors 22 and 36, and further, a voltage-producing section 34 serially connected between the conductor 36 battery 28) and the conductor 30 (armature Winding 14). Brieily, the regulating section 32 of the system operates to control the input to the voltage-producing section 34, whereby the voltage-producing section 34- modifies the battery voltage in a predetermined way. Actually, the section 34 supplies to the armature circuit repetitive D.C. pulses having constant amplitudes, each voltage pulse having a pulse width (or time duration) corresponding to the type of input signal developed by the regulating section 32.

Considering first the regulating section 32, it comprises an on-off switch 46 serially connected to a parallel branch circuit, the right branch of which develops the input signal which is fed to the section 34. It will be appreciated that when the switch 4t) is opened, no armature voltage is developed by the system l@ and, hence, the motor 12 is inoperative. However, when the switch 40l is closed, armature voltage may or may not be developed, depending upon the condition of the control system l@ and, in particular, the regulating section 32. yIn any event, the right branch of the parallel circuit, as seen in FIG. l, includes la variable resistor 42 of relatively high resistance serially connected to a shunt `arrangement comprising a resistor 44 and a capacitor 45, the junction of the variable resistor 42 and the shunt arrangement 44-46 being identied as 48. The left branch of the parallel circuit cornprises a resistor Sti serially connected with a vibrator 51 of a vibrator-diode arrangement 52 which functions to convert the D.C. voltage of the battery 28 into a pulsating voltage. The vibrator l more speciiically includes contacts 54, armature 53, and a serially connected ield coil 55 having its lower end connected to the positive terminal of the battery 23 via conductor 36. The contacts 54 are periodically opened and closed by the vibrator coil 1armature 53 in a manner well known to those skilled in the art. Specifically, upon closure of the manual switch 4l) current ilows in a path from battery 2S via the resistor Si), contact 54, armature 53 and eld coil 55 thereby generating a ilux in the core of the iield coil which attracts the armature 53 and interrupts the current path at the contacts 54. Thereupon, the ilux eld collapses permitting the current path again to be completed at armature 53 and contacts 54 and the dlux again to be generated in the core of the eld coil. Thus, the contacts S4 are opened and closed at a cyclic rate. A rectiiier 56 of the vibrator-diode #arrangement 52 is electrically connected between the junction of the armature 53 and the coil S5 and the junction 48.

It should be understood that, irrespective of the setting of the variable resistor 42, there is produced at the left side of the rectiiier S6, i.e., at the junction of the armature 53 and the coil 55, a pulsating voltage of reversing polarity (hereinafter called vibrator pulsating voltage) is developed by the electric energy building up and collapsing within the coil 55 in response to opening and closing of the contacts 54. The vibrator pulsating voltage is determined by the formula sa E Ndt where N is the number of turns in the coil 55 and is the time rate of change flux. Inasmuch as the contacts 54 are opened and closed quite abruptly, the time rate of change of flux is quite large and this in conjunction with the large number of turns in the coil 55 generates a pulsating voltage of a mangitude considerably greater than the magnitude B+ of the battery 28. As the resistor Sil is a relatively high impedance as compared to the irnpedance of coil 55, the base voltage at the junction between the armature 53 and the coil 55 will be at battery potential B+ and the voltage swing due to the vibrator pulsating voltage will be above and below battery potential B+. Because of the action of the rectiiier 56, only those portions of the vibrator pulsating voltage that are more positive than the DC. voltage at the junction 48 appear at that junction. The voltage at junction 4S is determined in part by the setting of the resistor 42.

Considering the operation of the regulating section 32 when the variable resistor 42 is set at its highest value, the composite voltage appearing at the junction 48 has the wave form illustrated in PIG. 3A. As shown, the voltage at junction 48 comprises a pulsating voltage at a level above the positive potential B+ of the battery 28. The composite wave `forni is as follows: at the moment of closing of the switch 4d, the quiescent voltage at the junction 4S is equal to the positive voltage B+ of the battery 28 inasmuch as resistor 42 is a very high impedance and substantially no current ilows through resistors 42 and 44. Accordingly, the condenser 46 has a substantially zero charge.

However, as soon as the vibrator 51 starts to produce its vibrator pulsating voltage above and below the quiescent voltage B+, positive peaks of vibrator voltage appear at the junction 48. The discharged condenser 46 charges to the value of the positive voltage peaks above the quiescent voltage B+ during the conduction period and then discharges toward B+ during the nonconduction period through resistor 44 as shown in FIG. 3A. Thus, when the variable resistor 42 is set at its maximum value, the

voltage of the junction 4S is a pulsating voltage always greater than the voltage B+ of the battery 28.

As the value of the resistors 42 is reduced, current ows through resistors 42 and 44 with the result that the yquiescent voltage at junction 48 decreases yfrom B+ toward zero, whereby the quiescent charge on the condenser 46 increases correspondingly from zero toward B+. 'Ihe quiescent voltage B+ at the junction of armature 53 and iield coil 55 remains unchanged so that at junction 48 the positive peaks and portions of the negative peaks of the vibrator pulsating voltage appear. rPhe charged condenser 46 then is discharged toward the maximum positive pulsating voltage at junction 4S and thereafter recharged toward the quiescent voltage at junction 48. Dependent upon the relative selected values of resistors 44 and Si)1 and the selected range of values Ifor resistor 42, the voltage at junction 48 can be made to vary cyclically above and below B+ in a variable duty cycle. FIG. 3B illustrates a Wave `form of the voltage yat junction 48 for a particular setting of the resistor 42.

From the foregoing description, it will be understood that by changing the setting of the resistor 42, there can be developed at the junction `48 a composite voltage that includes a pulsating component which is always positive with respect to the positive voltage B+ of the battery l2% or `a composite voltage which includes portions both positive and negative with respect to the positive voltage of the battery 28. In view of the fact that the resistor 42 can be set at an infinite number of values, the ratio of the negative and positive portions of the pulsating voltage can be adjusted and, more importantly, the relative time durations of the negative `and positive portions of the pulsating voltage can be varied.

The voltage-producing section 34 of the control system l@ operates to produce repetitive voltage pulses, in accordance with the composite voltage developed at the junction `4S by the section 32. Thus, the section 34, which is serially connected between the battery 2S and armature winding 14, functions to periodically open the above armature circuit, thereby to produce a plurality of pulses having an amplitude equal to the voltage amplitude of the battery 2S. The pulse Width of these pulses, and hence the average armature voltage, is controlled by the composite input signal developed by the section 32. Briey, the section 34 comprises a control transistor T-1 of the PNP type and a plurality of auxiliary transistors T-Z, T-3, T-4, T-S, and T-6 of the PNP type having their emitter-collector circuits connected between the battery 128 and the armature 14 via conductors 36 and 30. The control transistor T-l is periodically rendered conductive when the composite voltage at junction 48 has portions 80 (FIG. 3B) that are more negative than the positive voltage of the battery 28y and tas a result of the conduction of the control transistor T-l, the plurality of secondary transistors T-Z through T-6 are likewise rendered conductive.

More specifically, the base B-1 of the transistor T-1 is electrically connected to the junction 4g by conductor 5S so that the base B-ll is biased with respect to its emitter E-1 in accordance with the composite voltage appearing at the junction 48, the emitter Evi being electrically connected via a conductor 62 .and a resistor 6) to the conductor 36 to which the resistor yitis connected. As long as the base B-l remains positive with respect to the emitter E-l of the transistor T-1, no current tlows in the base-emitter circuit. However, when the base B-l becomes negative with respect to the emitter E-d, the base-emitter circuit conducts current with the result that a substantially greater current flows in the collector-emitter circuit of the transistor T-ll, the collector being electrically connected to the conductor Si). The collectoremitter circuit of the transistor T-l is as follows: the battery 28, conductor 36, resistor 60, conductor 612, emitter E-d, collector C-1, conductor 30, armature winding 14, conductor 1S, switch 20, field winding 16, conductor 22, and the battery 28. It will be appreciated that the collector-emitter circuit of the transistor T-l conducts current and, in essence, applies a voltage to the armature winding 16 whenever the base Bal of the transistor T-1 is negative with respect to the emitter E-l.

The plurality of secondary transistors T-Z through T-6 have their bases B-Z through B-6 respectively connected through resistors 64 to a conductor 66. The conductor 66 is connected to the junction of the conductor 62 and resistor 60 (and hence emitter E-l of the transistor T-1) through a shunt resistor 68 and capacitor 7). The emitters E-2 through E-6 of t-he transistors T-2 through T-6 are respectively connected through resistors 72 to the conductor 36. It will be appreciated that the capacitor 70 and the parallel resistor 68 comprise a wave-shaping network which 4functions to maintain the bases B-2 through B-6 slightly more positive with respect to the emitters E-2 through E-6 when the transistor T-1 is nonconductive. Without the capacitor '70, the bases B-2 through B-6 would be at substantially the same potential as the emitters E-2 through E-6 so that the transistors T-2 through T-6 would not be denitely nonconductive. However, with the capacitor 70, even though no voltage drop is developed across the resistor 60 when the transistor T-l is non-conductive, the parallel capacitor 7d and resistor 63 cause the voltage of the bases B-Z through B-6 to become slightly more positive than the emitters E-Z through E-6. Thus, since the bases B-2 through B-o are more positive than the emitters E-2 through E-6, the base-emitter circuits of the transistors E-'Z through E-G do not conduct current. However, in response to the conduction of the transistor T-l and current ow through its collector-emitter circuit, a voltage drop is developed across the resistor 6l) which drives the bases B-2 through B-6 negative with respect to the emitters E-Z through E-6. Consequently, current flows through the baseemitter circuits of the transistors T-Z through T-, with the result that a substantially greater current flow is obtained through the collector-emitter circuits of the transistors T-2 through T-6. Since the collectors C-Z through C-6 of the transistors T-2 through T-6 are also connected to conductor 30, the collector-emitter circuits o the transistors T-2 through T-6 are connected in parallel across the collector-emitter circuit of the transistor T-1. Accordingly, six parallel current paths through the transistors T-1 through T-6 are provided instead of only one current path through the transistor T-l.

`Considering the operations tof the circuit of FIG. l, it is assumed that the forward contacts 20a are closed, the motor lon-off switch 40 is open, the large variable resistor 42 is set at its maximum value that no voltage is applied to the armature circuit of the motor 12. If it is desired to start the motor 12, the motor on-oii switch 40 is closed, whereby the vibrator-diode arrangement 52 produces a composite voltage at junction 48. With the variable resistor 42 set at its maximum value, the voltage, shown in FIG. 3A, comprises a pulsating voltage more positive than the positive voltage of the battery 28. This voltage appears between the base B-1 and emitter E-l of the transistor T-1, whereby the base B-1 is biased positive with respect to the emitter E-l so that no current ows through the base-emitter circuit of the transistor T-il at any time. Accordingly, the control system produces no armature voltage and the motor 12 remains in an inoperative condition.

The motor 12 is actually started by adjusting the variable resistor 42 to decrease its value such that the lower peaks of the pulsating voltage conducted by therectilier 56 become negative with respect to the positive voltage of the battery 28, thereby to bias the base B-1 of the transistor negative with respect to the emitter EF1. These negative peaks are identified in FlG. 3B by reference numeral 80. Hence, during the time intervals that the base B-1 is negative with respect to the emitter E-l, the base-emitter circuit of transistor 'lf-1 conducts current, whereby the collector-emitter circuit of the transistor TA1 also transmits current to supply a voltage pulse to the armature circuit of the motor 12.

More particularly, when the collector-emitter circuit of the transistor T- conducts current, a voltage drop occurs across the resistor 6d, thereby making the emitter E-1 and the bases B-2, `B-ItLB-4, B-5 and B-6 more negative with respect to the emitters E2, E-, E4, E-S and E6. Consequently, current flows in the base-emitter circuits of transistors T-Z through T-6, with the result that substantially more current ilows through the collector-emitter circuits of transistors T-Z through T-6. Hence, when the lower peaks of the composite voltage at the junction 4S are more negative with respect to the positive voltage of the battery 28, the collector-emitter circuits of all of the transistors T-Z through T-6 are rendered conductive to provide a voltage pulse for the armature circuit of the motor 12.

It will be appreciated that when the upper peaks 82 of the composite voltage at the junction 48 are positive with respect to the positive voltage of the battery 2S', the base B-ll becomes positive with respect to the emitter E-1 and current flow in the base-emitter circuit of the transistor T-1 is stopped. Accordingly, conduction in the collectoremitter circuit of transistor T-l is stopped, whereby the voltage drop across the resistor 6i) becomes zero. Thus, the bases B-2 through B-6 of the transistors T-Z through T-6 do not remain more negative with respect to their associated emitters E-Z through E-6. Accordingly, the current ilow in the base-emitter circuits of the transistors T-2 through T-6 is stopped and the secondary transistors T-2 through T- become nonconductive. In short, the transistors T-1 through T-6 are rendered conductive to produce a positive armature pulse when portions of the composite voltage are negative with respect to the positive voltage of the battery 28 and are rendered nonccnductive to produce no armatured voltage when portions of the A.C. voltage are positive with respect to the positive voltage of the battery 28. y

Although the base to emitter voltage of the transistor T-1 is ysomewhat tot a clipped sinusoidal, as seen i-n FIGS. 3A and 3B, the base to emitter voltages of the transistors T-Z through T-6 are somewhat squa're wave, as indicated in FlG. 3C and the vol-tage supplied to they armature circuit `of the motor 12 is substantially square wave, as indicated in FG. 3D. irrespective of the exact wave torni applied to the armature circuit of the motor 12, the voltaoaavee 7 ageA pulses developed by the transistors T-1 through T-6 produce an average armature voltage (indicated by a dotted line) which causes the motor 12 to rotate at a predetermined speed. This result is obtained since the speed of the motor, as is well known, is directly proportional to the voltage `applied to its larmature winding.

If it be assumed that the variable resistor 42 is set so th-at the base-emitter voltage on the transistor T-1 is as illustrated in solid line in FIG. 3B, the motor 12 rotates at the predetermined speed. However, if it is desired to increase the speed of the motor 12, the resistor d2 is adjusted to further decrease its resistance. The decrease in resistance of the resistor 42 causes the entire level of the conducted pulsating voltage to be decreased with respect to the positive voltage of the battery 2S. Consequently, the base B-1 of the transistor T-1 is :driven negative with respect to the emitter E-1 for longer periods :of time. Accordingly, the time intervals ott conduction of the transistor T-1 is increased, with the result that the voltage drop across the resistor 60 in the collector-emitter circuit of transistor T-1 exists for greater periods of time whereby the bases B-Z through B-6 are rendered negative with respect to the emitters E-2 through E-6 for longer periods of time. Whereas the base-emitter `circuits were conductive for approximately ty percent of the time, as indicated in solid lines in FIG. 3C, the base-emitter circuits are now conductive for approximately' sixtyiive percent of the time as indicated in dashed lines in FIG. 3C. Consequently, the width of the voltage pulses sup- Y plied to the armature circuit 'of the rnotor 12 is increased,

as indicated by `dashed lines in FIG. 3D. Accordingly, the average armature voltage is increased from the level indicated by the dotted line to the level indicated by the dash-dot line. With an increase in the :average armature voltage, the speed of the motor 12 increases.

From the foregoing description, it will 'be appreciated that the speed of the motor 12 can be regulated and set at `any predetermined value by the simple expedient of adjusting the resistor 42. The resistor 42 controls the time intervals of conduction of the transistors T-l through T-6 and, accordingly, determines the width of the armature voltage pulses, which, kas indicated above, control the magnitude of the average yarmature voltage. The variable resistor 4t2 can be adjusted to produce an infinite number of resistance values, whereby an infinite number of moto-r speeds are obtainable.

For rapid acceleration of the motor or application of full motor power, the transistors T-1 through T-6 can be shorted or bypassed by Ian `acceleration switch S which is connected across conductors 39" and 36 by conductor 82, illustrated in dotted lines.

Considering now FIG. 2, the control system 10 may also be used with a motor of the shunt type. As illustrated, the control system 10 has substantially the identical construction as illustrated in FIG. l and is likewise embodied in the armature circuit of a shunt motor 112. The shunt motor 112 embodies an armature 114 that is serially connected via conductor 118 to the negative termjnal of the battery 28 .and via .conductor 130 to the control sys-tem 10 which is serially' connected to the positive terminal of the battery 28 via ya conductor 136. In addition, the motor 112 includes a eld winding 116 electrically connected iacross the battery 2S. Similar to the series motor 12, the motor 112 embodies a reversing switch 12d. However, in contrast to the switch 20, the reversing switch 120 has two forward positions, a forward low position for obtaining high ltorque and relatively low speed and a forward high position for obtaining a relatively higher speed and relatively lower torque. More particularly, the high forward contacts 2da and c operate to connect the iield winding end 116e to the negative terminal of the battery 28 and the eld winding end 11611 to the positive terminal of the battery 28 through a variable resistor 143 ganged to the variable resistor 42. The lower forward contacts Zeb and 20c connect the winding end 11Go to the negative terminal of the battery 28 and connect the winding end 116b directly to the positive terminal of the battery 28. On the Iother hand, the reversing contacts 20d and 20e connect the winding end 11617 to the negative terminal of the battery 28 and the winding end 11Go to the positive terminal of the battery 28.

The control system 10 is identical in construction to the control system described, with the exception that the variable resistor 42. is ganged with the variable resistor 143 yassociated with the forward and reversing switch 120. In the interest of avoiding unnecessary repetition, the same reference numerals are used to identify the identical components in the control system `illustrated in FIG. 2 `as is illustrated in FIG. 1. Furthermore, the control system 1t? operates identically to the manner described :above and regulates the speed of the motor 112 by the simple expedient fof adjusting the variable resistor 42 and also the ganged resistor 143.

For rapid acceleration of the motor 12 or application of full rnotor power, the transistors T-l through T-6 can be bypassed or shorted by means of a switch which is `connected similarly to switch S0, across conductors 13G and 136 by a conductor 132' illustrated in dotted lines. In order to provide regenerative braking for the shunt motor, the transistors T-l through T- can be shunted with a back rectifier, identified by reference numeral 19o, associated switch 192, and resistor 194, the above arrangement being connected between conductors 13dand 136 via conductor 132.

While the embodiments described herein are at present considered -to be preferred, it is understood that various modifications and improvements may be made therein, and it is intended to cover in the appended claims all such modications and improvements yas fall within the true spirit and scope of the invention.

What is desired to be claimed and secured by Letters Patent of the United States is:

1. A speed regulating system for an electric motor comprising a power source, a voltage path from said power source through the armature of said motor, an electron ow device including Ian input electrode and and output electrode and a control electrode for selectively completing and interrupting said voltage path, a source of variable fixed bias including a charging capacitor across the input electrode and control electrode of said ilow device for controlling the amount of cut-oil bias applied to said electron ilow device, and a source lof cyclically varying signal applied across said input electrode and said control electrode for bucking said cut-olf bias and for controlling said electron ilow device to cyclically complete said voltage path.

2. A speed regulating system for an elect-ric motor comprising a power source, -a voltage path from said power source through the armature of said motor, an electron flow device including an input electrode and an output electrode and ra control electrode for selectively completing and interrupting said voltage path, a source of variable iixed bias including a parallel resistor and capacitor across said input electrode and said control electrode `and a variable resistor in series therewith across said power source for controlling the amount of change on said capacitor and accordingly the lamount of cutoff bias applied to said electron flow device, a unidirectional conducting device, and a source of cyclically varying signal yapplied across said input electrode and said control electrode via said unidirectional conducting device for bucking said cut-off bias and for controlling said electron ow device to cyclically complete said voltage path.

3. A speed regulating system for an electric motor comprising `a power source, a voltage path from said power source through the armature of said motor, an electron flow device including an input electrode and an output electrode and a control electrode for 'selectively 9 completing and linterrupting said voltage path, a source of variable iixed bias including a parallel resistor and capacitor across :said input electrode and said control electrode and a variable resistor in series therewith across said power source for controlling the amount of change on said capacitor and accordingly the `amount of cutoff bias applied to ysaid electron ilow device, a unidirectional conducting device, and a vibrator arrangement across :said power source providing -a cyclically varying signal between said input electrode and said control electrode via said unidirectional conducting device yfor bucking said cut-olf bias and for controlling said electron ilow device to cyclically complete `said voltage path, so that with said variable resistor at maximum resistance said capacitor is substantially dischanged and said electron ilow device is held continuously at cut-off and with said variable resistor at other resistance values said capacitor is charged accordingly and corresponding peak portions `of lsaid cyclically varying signal overcome said cut-oil bias and complete said voltage path for corresponding periods.

4. The speed regulating system `set forth in claim 3 wherein said voltage path includes multiple low impedance parallel paths controlled from said electron flow device for providing instantaneous voltage control to said arm-ature during each of the voltage path completion periods.

References Cited in the file of this patent UNITED STATES PATENTS 2,549,654 Wittenburg Apr. 17, 1951 2,707,261 Prior Apr. 26, 1955 2,780,763 Hertwig et al. Feb. 5, 1957 

1. A SPEED REGULATING SYSTEM FOR AN ELECTRIC MOTOR COMPRISING A POWER SOURCE, A VOLTAGE PATH FROM SAID POWER SOURCE THROUGH THE ARMATURE OF SAID MOTOR, AN ELECTRON FLOW DEVICE INCLUDING AN INPUT ELECTRODE AND AND OUTPUT ELECTRODE AND A CONTROL ELECTRODE FOR SELECTIVELY COMPLETING AND INTERRUPTING SAID VOLTAGE PATH, A SOURCE OF VARIABLE FIXED BIAS INCLUDING A CHARGING CAPACITOR ACROSS THE INPUT ELECTRODE AND CONTROL ELECTRODE OF SAID FLOW DEVICE FOR CONTROLLING THE AMOUNT OF CUTT-OFF BIAS APPLIED TO SAID ELECTRON FLOW DEVICE, AND A SOURCE OF CYCLICALLY VARYING SIGNAL APPLIED ACROSS SAID INPUT ELECTRODE AND SAID CONTROL ELECTRODE FOR BUCKING SAID CUT-OFF BIAS AND FOR CONTROLLING SAID ELECTRON FLOW DEVICE TO CYCLICALLY COMPLETE SAID VOLTAGE PATH. 